1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer.
2. Description of the Related Art
Heretofore, as an image forming apparatus such as a laser printer, there has been known one which includes a cassette capable of accommodating a plurality of sheets of paper in a stacked state, below the apparatus proper, and a paper ejection tray for ejecting the sheet of paper formed with an image, above the apparatus proper.
In such an image forming apparatus, the uppermost sheet of paper within the cassette is delivered toward the front side of the apparatus proper. Besides, the sheet of paper delivered from the cassette has its conveyance direction turned into the opposite direction at the front end part of the apparatus proper, it is conveyed toward the rear side of the apparatus proper along a conveyance path which extends in a front and rear direction above the cassette, and it is formed with the image while being conveyed along the conveyance path. The sheet of paper formed with the image has its conveyance direction turned into the opposite direction again at the rear end part of the apparatus proper, and it is ejected from behind the paper ejection tray by the paper ejection tray.
The conveyance path is provided so as to be substantially horizontal or to somewhat incline upwards toward the rear side. Therefore, a space appears between the conveyance path and the cassette, and a control circuit board and a power-source circuit board are arranged in the space, whereby the effective utilization of the space within the apparatus proper is attained (refer to, for example, JP-A-7-143300 and US2004/0095456A1).
In an image forming apparatus of electrophotographic scheme, a scanner unit for high-speed scanning with a laser beam based on image data, and a process cartridge including a charger, a photosensitive drum, a developing roller, a transfer roller, a cleaner, etc. are disposed in the apparatus proper.
In such an image forming apparatus, a high-voltage power-source circuit board which applies an electric-discharge bias, developing bias, transfer bias and cleaning bias to the charger, developing roller, transfer roller and cleaner, respectively, is disposed, and a gear plate which supports a motor for rotationally driving the photosensitive drum, developing roller, transfer roller, etc., and a gear transmission mechanism for transmitting driving forces is disposed.
There has been proposed an image forming apparatus wherein an engine-drive circuit board including a high-voltage power-source circuit portion, and a motor and a drive portion are vertically arranged on body side surfaces which are on opposite sides to each other (refer to, for example, U.S. Pat. No. 6,778,197B1).